At one point she let out "the most unmerciful scream" he had heard. Later, the family discovered that a nurse had given her only 20ml of Calpol to ease the pain.

Miss McNicholas, 20, a customer services clerk from Widnes, Cheshire, died after falling into a diabetic coma in July 1997.

The previous year her GP, Dr Neil Martin, identified her as having diabetes. However, when she went to him before going on holiday to Prestatyn, North Wales, he allegedly told her she had an under-active thyroid gland.

Miss McNicholas began vomiting in Prestatyn, where a local GP, Dr John Hughes, said she had gastritis.

The same diagnosis was given by a locum after she returned to Widnes. Dr Martin confirmed his colleagues' opinions when he saw Miss McNicholas on July 21.

But later that day she was taken to Halton General Hospital, where a specialist correctly diagnosed her as suffering from diabetic ketoaciditis. Miss McNicholas fell into a coma and died on July 31, 1997.

The Cheshire coroner, Nicholas Rheinberg, halted an earlier inquest because a juror knew one of the doctors involved. The new hearing is expected to last five days.

Mr McNicholas recalled seeing his sister "in a terrible condition" in intensive care. "To touch her she felt like ice, and I mean like ice," he said. "You could have chilled a drink on her."

Mr McNicholas said a doctor spent 30 minutes trying to take a blood sample while she writhed in agony.

"She looked at me straight in the eye and said: 'Michael you don't know what they are doing to me.' And I didn't but she allowed them to continue.

"At about quarter to eight in the evening Sarah Jane was talking to my parents and to Terry, her fiance. I was there as well and all of a sudden she let out the most unmerciful scream I have ever heard. She was twitching and kicking off the bed covers."

Shortly afterwards the family members were ushered out of the unit and told to return the following morning when they would find "a totally different girl". But by then Miss McNicholas had lost consciousness for the last time.

Her brother said Dr Ali Khaleeli, a diabetes specialist, insisted that her loss of consciousness had nothing to do with her diabetes. "He said he didn't understand what was going on and went on to tell us what a wonderful doctor he was."